Over the years there has been considerable interest in the possibility of using tunnel-injection of minority carriers into direct-gap semiconductors as an alternative to a p-n junction in electroluminescent devices. Previous attempts to fabricate metal-insulator-semiconductor (MIS) tunneling structures with various III-V and II-VI compound semiconductors generally resulted in devices which were inefficient injectors. In many cases, these devices required voltages large compared to the bandgap so that impact ionization rather than tunneling may have been the source of the minority carriers. Lack of a good native oxide has hindered fabrication of good tunneling devices on compound semiconductors. Descriptions of some of those prior devices are presented in:
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